Article packaging machines that arrange articles, such as food and beverage cans and bottles, into groups of desired sizes and configurations, and place those article groups into paperboard or corrugated board cartons, are well known. In some types of packaging machines, the packaging operations may be performed simultaneously, while in others they may be performed sequentially, enabling the packaging of article groups into cartons at rates of hundreds of cartons per minute. It is not uncommon, for example, for packaging machines to operate at production rates of two hundred cartons per minute to three hundred cartons per minute, and higher. Packaging machines utilize a variety of techniques to group articles to be packaged depending generally on the type of machine and the kind of carton used. Some machines, for instance, place articles into a sleeve-type carton, usually by forming the sleeve from a carton blank, grouping the articles, and pushing or sliding each group of articles into an open sleeve, which is then closed at each end. Other machines may place basket-type cartons over an article group, and then close the carton along its bottom side to complete the packaging operation. Still other machines may form articles into groups, and then wrap a paperboard carton blank around each group of articles to form a completed package. These wrap-type cartons can include features that allow the opposed ends of the carton to cooperate to form a locking mechanism that holds the wrap-type carton together around each group of articles. Glue or other chemicals can be used to bind carton surfaces to one another in any type of carton, either alone or in conjunction with mechanical carton locking features, such as tabs and slots.
An important feature of most, if not all, types of carton packaging machines is the use of conveyor systems that move large numbers of articles, carton blanks, the formed cartons, and finally the packaged cartons, through the machine. Common types of article conveyor systems include a plastic or rubber endless belt-type conveyor that supports the articles and moves them downstream. Other conveyor systems may include moving pressure belts positioned on either side of a lane of articles that are supported on a stainless steel plate known as a dead plate. The pressure belts contact opposite sides of the articles and force the articles downstream across the dead plate to a downstream position of the machine. Conveyor systems of packaging machines can include chains with lugs or teeth that contact the articles as they are conveyed in order to meter the article spacing for a next step in the packaging operation. Conveying systems may also include mechanical paddles in the form of wedges driven by a chain or belt that contact the articles and thus select or “pick” a desired number of articles from a larger group, and move them downstream to the next work station.
Since speed of operation is an essential quality of article packaging machines, such machines are designed to perform certain functions simultaneously and in sync with other functions, so that the operations of the machine are as continuous as possible, and thus the name “continuous motion” packaging machines. Even during normal operation of some types of continuous motion packaging machines, however, a machine operator must stop the machine from time-to-time to reposition or remove articles, effect a component change-over, or to perform other functions. Machine stoppage, however, can seriously adversely affect machine productivity and output, and so it is advantageous to reduce the time of machine stoppage or even eliminate certain functions, if possible, that require a machine to be stopped during a production run. One operation that traditionally has caused machine stoppages and manual intervention is the cleaning out or otherwise dealing with the last few trailing articles of a production run, which do not tend to convey smoothly through the machine by themselves, as discussed in more detail below.
Packaging operations are designed considering the predictable movement of articles to be packaged along a path of travel through the machine, from an upstream end to a downstream end at a predetermined rate of speed. A sizeable quantity of articles, which can be thousands or tens of thousands of articles, that are intended to be packaged in a single production run are fed either automatically or manually onto a product intake table. This table can take the form of an active conveyor that moves the large group of articles toward working stations of the machine. Alternatively, the table may take the form of a large smooth plate of, for example, polished stainless steel or plastic, commonly referred to as a “dead plate” since the plate itself does not apply a force to move the articles downstream. In either case, the table may be, for example, 10 to 20 feet wide and as long as necessary, for example 20 feet long. The table typically tapers to a reduced width as it approaches the packaging machine in order to corral the many generally disorganized articles on the table into a reduced number of articles across the width of the table. At some point, steel or hard plastic upstanding guide rails further downstream corral the articles into the desired numbers of aligned article infeed lanes such as, for example two separate side-by-side infeed lanes of articles.
In many types of infeed systems, the articles are conveyed toward the machine by a conveyor belt that supports the articles the entire distance to the workstations of the packaging machine. When the articles are divided into, for example, two separate lanes, the conveyor may only be slightly wider than the total width of the articles, for example a common 12 ounce beverage can.
Depending upon the type of packaging machine used, the machine can include various zones, or lengths along the path of downstream article travel, where the articles have no active conveying mechanism. These zones are sometimes referred to as “dead zones” or “dead plates.” It is not uncommon for certain types of continuous motion packaging machines to include two or more dead zones located between machine stations where a packaging activity is taking place. One such packaging machine is manufactured and sold, in various models, by Graphic Packaging International, Inc. of Marietta, Ga., under the brand name Marksman®. Marksman® machines are known in the trade as “wrap-type packaging machines.” Wrap-type packaging machines intake articles (e.g. beverage cans), corral and divide the articles into single file side-by-side infeed lanes of a selected number, for example two separate lanes, and convey the articles along the infeed lanes to and through various work zones where packaging activity occurs. Within the work zones, the articles may be metered by, for example, pressure belts or conveyor belts, so that the articles are positioned correctly as they enter the subsequent work zones. In other work zones, a carton blank may be placed over and around an article group to “wrap” the group with the carton blank and hold the articles of the group securely together. In other work zones, moving pressure belts may engage the sides of wrapped groups of articles to move the wrapped groups away from the wrapping area and downstream to be removed from the machine.
In Marksman® brand and other packaging machines, there typically are dead zones that exist between or that are otherwise associated with certain work zones or stations where the articles are not actively conveyed. For example, there may be a dead zone or dead plate under the article lanes between the intake conveyor and the metering belts. Another dead zone may exist downstream of the metering belt, in the region of the wrapping station. Other dead zones are possible along the path of travel of the articles as they move in single file lanes throughout machine. As long as there is a constant stream of articles moving through the machine and through the various work zones, the articles are pushed across the dead zones by articles upstream behind them, which are being actively conveyed along the path. However, at the end of a production run when the last or trailing groups of articles approach the work zones of the machine, there are no articles up stream to push the remaining articles across the dead zones between work stations. As a consequence, articles can become stuck or stalled within one or more dead zones, which disrupts the packaging functions of the machine.
Under these circumstances, some machine operators simply stop the packaging machine, remove the few articles of a production run from the machine, and either discard them or use them in another run, if possible. Other operators prefer not to create such product “waste,” and so utilize a system to push the final queue of articles in a production run through the machine so that they can be packaged. Typically, the packaging machine is stopped or deactivated by the operator and placed into a “clean out mode.” In the clean out mode, the machine is generally caused to move to a “clean out initiating point,” typically identified when the end of the product queue has passed sensors positioned adjacent the downstream end of the infeed conveyor. The machine operator then manually removes a number of articles, for example, beverage cans, up to a specific point on the infeed conveyor. The remaining number of articles are sufficient so that the articles remaining on the infeed conveyor are the correct number needed to completely fill the last carton or cartons in the production run.
With the proper number of articles remaining in the queue, the operator manually places a specially designed device, referred to as a “follower slug” or follower, on the infeed conveyor. The follower can be of any suitable construction, but typically is comprised of a synthetic material, such as an elongate nylon block, sized to be the same approximate width as the articles being packaged and including the same side edge profile as the articles (e.g. cans or bottles). The follower may be made to be weighted heavier along its rearward end section and lighter along its forward end section. The operator then may place a number of “dummy cans” in the lanes of the machine between the last article (can) in the queue and the follower. The follower is long enough to extend onto the infeed conveyor, so that as the conveyor moves forwardly, the follower is actively conveyed by the conveyor and pushes the dummy cans in the downstream direction toward, for example, the metering belt station if the machine is a Marksman® packaging machine. The dummy cans, in turn, push the articles in front of them downstream through and past the work stations such as the metering station and into the successive work stations, which, in the Marksman® machine may be the wrapping station etc. The machine then is operated to cycle the appropriate number of cartons, stopping the feeding of cartons at the appropriate time, so that the last of the cartons corresponds to the entry of the follower. At this point, the machine stops moving when the follower and its corresponding carton have reached a certain point, where a compression belt is located. The machine is then deactivated.
At this position, the machine operator opens a guard cabinet that surrounds the machine's working components, and removes the follower. The operator then restarts the machine in a “clean out mode,” wherein the machine cycles the appropriate number of cartons until all cartons have been loaded and the machine stops. The operator then opens the guard doors and removes the cartons containing dummy cans, which have themselves been packaged during the clean out mode. It can be appreciated, therefore, that a substantial amount of operator effort and time is required to move the trailing articles of a production run through the machine to be packaged. This process, while effective, interrupts the machine and thus causes downtime in the machine operation, which in turn adversely affects productivity, or number of cartons per unit time.
Therefore a need exists for automation in the movement of the last or trailing group of articles of a production run through the various working stations of a packaging machine and across associated dead zones so that all articles of the production run are packaged without operator intervention or machine down time. More generally, a need exist for a method and apparatus for pushing trailing articles of a production run through packaging machines and, indeed, through other types of production machines where large number of articles are conveyed through work zones of the machine. It is to the provision of such a method and apparatus that the present invention is primarily directed.